Pain, the universal human experience, has been the focus of intense efforts to improve its management in ill clinical populations for years, but sadly, many people continue to suffer with inadequately managed pain. Good assessment is fundamental to managing pain, and is based on individual self-report because pain is subjective. People who cannot communicate their pain because of underlying medical conditions and treatments are at higher risk for unrecognized pain, unnecessary suffering, additional co-morbidities, poorer quality of life, and prolonged healing and recovery. Many of these individuals are receiving palliative care, which is now delivered in tertiary acute, hospice, long term, and home care settings. A major emphasis is pain management, yet no satisfactory pain assessment tools are available for non-communicative palliative care patients with pain. The research team's preliminary studies of the Multidimensional Objective Pain Assessment Tool (MOPAT), which uses behavioral and physiological indicators to assess pain, demonstrate initial evidence of reliability and validity. The specific aims of this study are to: 1) test the reliability and validity of the MOPAT for assessing acute pain in non-communicative patients in three different types of palliative care settings: 1) inpatient tertiary acute care hospital, 2) inpatient community hospice, and 3) inpatient Veterans Administration hospice; and 2) appraise the clinical utility of the MOPAT when used by nurses to assess acute pain in non-communicative patients in two different types of palliative care settings: 1) inpatient tertiary acute care hospital, and 2) inpatient community hospice. Using a methodologic design, the researchers will test the tool in 130 acute care inpatients (pre- and post-pain medication intervention) and 100 hospice inpatients (longitudinally for duration of admission) using observations by pairs of raters. Extensive demographic, clinical, and treatment data will also be collected. The analyses will use Generalizability Theory to evaluate reliability, a theoretical approach and causal measurement theory to evaluate validity, and descriptive statistics and mixed modeling to evaluate clinical utility. If this study is successful, knowledge of how to assess pain in this vulnerable population will be advanced. It should help facilitate the management of pain in non-communicative patients across palliative care settings and ultimately result in less suffering. [unreadable] [unreadable] [unreadable]